#include<stdio.h>

#include <unistd.h>
#include <stdlib.h>

int main()
{
 pid_t id=fork();

 if(id==0)
 {
    int* p=NULL; 
    printf("I am child process,pid:%d,ppid:%d\n",getpid(),getppid());
    *p=2; 
 }

  sleep(2);
  printf("I am father  process,pid:%d,ppid:%d\n",getpid(),getppid());
  
  return 0;
}

//int main()
//{
// pid_t pid;
// printf("Before: pid is %d\n", getpid());
// if ( (pid=fork()) == -1 )perror("fork()"),exit(1);
// printf("After:pid is %d, fork return %d\n", getpid(), pid);
// sleep(1);
// return 0;
//} 
